Carbohydrates

Question 1

What do monosaccharides serve as?

Answer 1

Monomer units which make up larger carbohydrate

Question 2

What is a hexose sugar?

Answer 2

A monosaccharide which is made up of 6 carbon atoms in each molecule

Question 3

What is a precipitate?

Answer 3

2 solutions that make up a solid.
Solid particles suspended in a solution.

Question 4

Why does amylopectin have side branches?

Answer 4

Allow enzymes break down molecule to get at the glycosidic bonds easily.
= glucose released quicker

Question 5

Explain the biochemistry of animals and plants (evolution)

Answer 5

All contain same groups of C based compounds that interact in similar way.

Question 6

What does a plant do when needs more glucose/ energy?

Answer 6

Breaks down / hydrolisis starch to release glucose for respiration

Question 7

What gives amylose a coiled structure?

Answer 7

Angles of glycosidic bonds

Question 8

What do the hydrogen bonds form in cellulose?

Answer 8

Strong fibres = microfibrils

Question 9

Why is starch good for storage?
2 marks

Answer 9

Insoluble
So doesn’t affect water potential so it doesn’t cause water to enter by osmosis, which would make it swell

Branched coiled make compact = store more smaller space
Branched = enzymes, fast breakdown

Question 10

What polysaccharide is made from 3 alpha glucose molecules?

Answer 10

Amylose

Question 11

When testing for sugar what does it mean if:
A) it turns blue first time testing
B) if turns green, yellow, orange, brick red second time
2 marks

Answer 11

A) there are no reducing sugars present but possibility that non reducing sugar is present

B) it is non reducing

Question 12

Why would you connect a glycosidic bond at the top?

Answer 12

As the OH needed for the reaction is at top rather than bottom. So can’t connect next to each other.

Question 13

How do you separate polysaccharide into monosaccharides?
(In diagrams)

Answer 13

Split glycosidic bond and add H on either side.

Question 14

A precipitate is produced in a positive result for reducing sugar in a Benedict’s test.
A precipitate is solid matter suspended in solution.
A student carried out the Benedict’s test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution.
1 mark

Answer 14

Filter and dry the precipitate. Find weight/ mass

Question 15

Lactulose is a disaccharide formed from one molecule of galactose and one molecule of fructose.
Other than both being disaccharides, give one similarity and one difference between the structures of lactulose and lactose.
2 marks

Answer 15

Similarity - both contain glycosidic bond/ galactose

Difference - lactulose contains fructose, while lactose contains glucose

Question 16

During early pregnancy, the glycogen in the cells lining the uterus is an important energy source for the embryo.
Suggest how glycogen acts as a source of energy.
Do not include transport across membranes in your answer.
2 marks

Answer 16

1. Hydrolysed ( to glucose )
2. Glucose used in respiration

Question 17

Describe structure of glycogen

2 marks

Answer 17

Polymer of alpha glucose
Branched structure
Joined glycosidic bonds

Question 18

A student wanted to produce a dilution series of a maltose solution so he could plot a calibration curve. He had a stock solution of maltose of concentration 0.6 mol dm-3 and distilled water. He made a series of dilutions from 0.1 to 0.6 mol dm-3.
Complete the table below

First row
A) Concentration units?
. Volume 0.6moldm3 maltose solution cm3
B) what is third row box name and units

Second row
A) conc of maltose?
. 5moldm3 volume maltose
. 10 vol of ?

(2 marks)

Answer 18

First row
A) mol dm-3
B) volume of water / cm3

Second row
A) 0.2
. ? =vol of water

Question 19

Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function.
Explain one way in which starch molecules are adapted for their function in plant cells.
2 marks

Answer 19

Insoluble;
Don’t affect water potential;

Helical and compact

Question 20

Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers.

Give two named examples of polymers and their associated monomers to illustrate answer.
5 marks

Answer 20

A condensation reaction joins monomers together and forms a (chemical) bond and releases water;
A hydrolysis reaction breaks a (chemical) bond between monomers and uses water;

Examples include:
Amino acid to protein
Alpha glucose to starch/glycogen
Beta glucose to cellulose
Nucleotide to DNA/RNA

A second suitable example of polymers and the monomers from which they are made;

Reference to a correct bond within a named polymer ( glycosidic)

Question 21

Name three disaccharides and for each one, state monosaccharide constitutes?

Answer 21

Maltose - 2 glucose molecules

Sucrose - glucose and fructose

Lactose - glucose and galactose

Question 22

Is ATP made/produced during photosynthesis and respiration?

Answer 22

Yes

Question 23

How is starch (amylose and ampectin) a compact molecule

Answer 23

Amylose - As it is coiled (due to angles in glycosidic bonds)

Amylopectin- or branched

Question 24

Explain how cellulose molecules are adapted for their functions in plant cells. (3 marks)

Answer 24

(1) Long and straight chains;

(1) Become linked together by many hydrogen bonds to form fibrils;

(1) Provide strength (to cell wall).

Question 25

Lactulose can also be used to treat people who have too high a concentration of hydrogen ions (H+) in their blood.

The normal range for blood H concentration is 3.55 times 10 to power of -8 to 4.47 times 10 to power of -8

A patient was found to have a blood H+ concentration of 2.82 times 10-7 mol dm-3

Calculate the minimum percentage decrease required to bring patient’s blood H+ conc into its normal range

2 marks

Answer 25

Percentage change = final value - original value
Divided by original
Times of 100

2.82 times 10-7 - 4.47 times 10-8
Answer of that divided by 2.82 times 10-7

= 84. 14 %

You take away form 4.47 … because it is the minimum / closest number to get blood back into normal range